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I have considerable experience with 'bio-diesel" especially blends that are from 'reclaim' (cooking oils, etc.).
If you keep the 'blend' to no more than 10% bio-diesel or 'reclaim', chemical compatibility usually is no problem, 15% being the upper limit. This will insure that the typical Buna/Neoprene elastomers of hosing, valve seats and diaphragms, etc. will (somewhat) stay integral for beyond 'short term exposure'.
Beyond 10-15% one really needs to consider Teflon, elastomeric teflon co-polymers, or Viton; .... this includes changing from polypropylene to nylon, UHMWPE, etc. for tankage, etc.
For 'reclaim', that is co-contaminated with oleic and other organic acid forms use only Teflonics (PFA, PTFE, ECTFE. etc.). This includes engine crankshaft, etc. seals, etc. as the normal engine blow-by containing oleic, etc. acid will also soon soften/destroy the Buna/Neoprene engine lube-oil seals, seals on common lube oil recirc. filters/filter housings, oil pan and valve cover gaskets, etc. etc. Also keep the intake (and to some extent exhaust) valve seals under close scrutiny, especially if the 'wiper' section is of OEM BUNA/Neoprene.
10% bio-diesel usually isnt a problem; greater than 15% usually requires quite expensive 're-sealing' and re-gasketing. If using 'reclaimed' cooking oils, the oleic acid component can, on long term, attack the OEM polymer seals, etc. as low as 5% if the fuel is stored/heated to much above 30°C.
PTFE/PFA/ECTFE based or Viton seals are horrendously expensive in comparison to the standard BUNA/Neoprene. PFA/PTFE seals also require perfectly smooth shafting journals, etc.